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Biomedical subjects

Michael Weber

Publications and source records attributed to Michael Weber.

At least 55 records · Page 3Linked to original sources
PubMed2005

Characterization of benign and malignant breast lesions with computed tomography laser mammography (CTLM): initial experience.

OBJECTIVES: The aim of this study was to characterize benign and malignant breast lesions with computed tomography-laser mammography (CTLM). MATERIALS AND METHODS: In a prospective study, 100 female patients with 105 breast lesions classified as BIRADS IV to V at mammography underwent mammography, CTLM, and histologic verification at our institution. CTLM images were analyzed by radiologists with knowledge of the lesion's position but who were blinded to histology and morphologic findings from mammography. Two radiologists independently evaluated whether there was increased absorption, a sign of malignancy, on CTLM and assessed the appearance (volumes or linear branching) and shape (round or irregular) of the lesions. RESULTS: Histologic analysis revealed 55 benign (52.4%) and 50 malignant (47.6%) breast lesions. Increased absorption was observed significantly more often in malignant than in benign lesions (70.0% vs. 32.7%, P = 0.028). Invasive cancer showed increased absorption in 76.2%, and ductal carcinoma in situ in 37.5%. Common morphologic characteristics of increased absorption were "volumes" (85.7% of malignant and 77.8% of benign lesions) with round shape (78.1% of malignant and 73.3% of benign lesions). CONCLUSION: Our data indicate that CTLM, when used as an adjunct to mammography, may provide additional information to characterize benign and malignant breast lesions.

Adolescent↗
PubMed2005

Flat-panel-detector chest radiography: effect of tube voltage on image quality.

PURPOSE: To compare the visibility of anatomic structures in direct-detector chest radiographs acquired with different tube voltages at equal effective doses to the patient. MATERIALS AND METHODS: The study protocol was approved by the institutional internal review board, and written informed consent was obtained from all patients. Posteroanterior chest radiographs of 48 consecutively selected patients were obtained at 90, 121, and 150 kVp by using a flat-panel-detector unit that was based on cesium iodide technology and automated exposure control. Monte Carlo simulations were used to verify that the effective dose for all kilovoltage settings was equal. Five radiologists subjectively and independently rated the delineation of anatomic structures on hard-copy images by using a five-point scale. They also ranked image quality in a blinded side-by-side comparison. Average ranking scores were compared by using one-way analysis of variance with repeated measures. Data were analyzed for the entire patient group and for two patient subgroups that were formed according to body mass index (BMI). RESULTS: The visibility scores of most anatomic structures were significantly superior with the 90-kVp images (mean score, 3.11), followed by the 121-kVp (mean score, 2.95) and 150-kVp images (mean score, 2.80). Differences did not reach significance (P > .05) only for the delineation of the peripheral vessels, the heart contours, and the carina. This was also true for the subgroup of patients (n = 24) with a BMI greater than and the subgroup of patients (n = 24) with a BMI less than the mean BMI (26.9 kg/m(2)). At side-by-side comparison, the readers rated 90-kVp images as having superior image quality in the majority of image triplets; the percentage of 90-kVp images rated as "first choice" ranged from 60% (29 of 48 patients) to 90% (43 of 48 patients), with a median of 88% (42 of 48 patients), among the readers. CONCLUSION: Delineation of most anatomic structures and overall image quality were ranked superior in digital radiographs acquired with lower kilovoltage at a constant effective patient dose.

Aged↗
PubMed2005

Flat-panel display (LCD) versus high-resolution gray-scale display (CRT) for chest radiography: an observer preference study.

OBJECTIVE: Our objective was to compare cathode ray tube (CRT) display with liquid crystal display (LCD) for soft-copy viewing of chest radiographs in a clinical setting. MATERIALS AND METHODS: We displayed 80 posteroanterior digital chest radiographs side by side on a 5-megapixel CRT display and a 3-megapixel LCD. Gradation characteristics of both monitors were adjusted to DICOM display standards. Using a 4-point scale, seven radiologists ranked overall image quality and visibility of anatomic landmarks. Data analysis included Wilcoxon's rank sum test to assess the significance of preference for the different display modes and calculation of the percentage of images ranked equally by at least five of the seven radiologists. RESULTS: Wilcoxon's rank sum test found significant preferences (p < 0.001) for the CRT display for visualization of structures in low-attenuation areas of the thorax and for the LCD for visualization of structures in high-attenuation areas of the thorax. Overall image quality was ranked equal by at least five radiologists in 70% of cases, whereas for the remaining images a significant preference was found for the CRT display. CONCLUSION: We conclude that, under subdued ambient lighting conditions and without use of windowing, for most images the overall quality is equal with high-resolution CRT display and LCD. In images judged preferentially, we found a significant superiority for LCD for delineating mediastinal structures and for CRT display for delineating structures in the lung.

Computer Terminals↗
PubMed2005

Chronotherapeutic oral drug absorption system verapamil is effective in reducing morning blood pressure in African Americans: a post hoc analysis of the chrono trial.

Results of several clinical trials have shown that verapamil is effective in reducing blood pressure (BP) in African Americans, a population at high risk for hypertension and target-organ damage. Nonetheless, adequate control of BP is perceived as difficult to achieve in this population. A post hoc analysis of data from the community-based CHRONO trial (Controlling Hypertension in the moRning with a ChrONO medication) was undertaken to assess racial/ethnic differences in the safety and efficacy of the Chronotherapeutic Oral Drug Absorption System (CODAS) formulation of verapamil in a real-world setting. Once-daily administration of the CODAS formulation of verapamil significantly reduced morning BP (P<0.0001) regardless of race or ethnicity. In the African-American population (N=466), the response rate for systolic BP (<140 mmHg or > or =10% reduction from baseline) and diastolic BP (<90 mmHg or reduction > or =10 mmHg from baseline) combined was 70.8%, and 60% of those individuals responded at the lowest (200 mg) dose. Of the 59.7% of African Americans who reached the target BP of <140/90 mmHg, 64% did so at the 200-mg dose. Response rates were not affected by gender, age or treatment history, and CODAS-verapamil was well tolerated in all ethnic/racial treatment groups. In a trial conducted in actual clinical practices, the CODAS formulation of verapamil was shown to be safe and effective in African Americans, Caucasians, Hispanics and Asians.

Administration, Oral↗
PubMed2004

Detectability of catheters on bedside chest radiographs: comparison between liquid crystal display and high-resolution cathode-ray tube monitors.

PURPOSE: To compare observer performance with a flat-panel liquid crystal display (LCD) monitor and with a high-resolution gray-scale cathode-ray tube (CRT) monitor in the detection of simulated support catheters on bedside chest radiographs. MATERIALS AND METHODS: The ethics committee did not require approval or patient informed consent when this study began. Because of a change in regulations, before images were acquired the nature of the study and procedures were explained to patients or their relatives, and consent was then obtained. A total of 131 catheter fragments (12-14 per radiograph) were superimposed over 10 anteroposterior bedside chest radiographs obtained with storage phosphor technology. Images were displayed on an LCD monitor (1536 x 2048 matrix) and a CRT monitor (2048 x 2560 matrix). Five radiologists independently located the catheter fragments and rated their confidence in detection with bright and subdued ambient light. A two-way analysis of variance and the Friedman test were used for statistical analysis. RESULTS: There was no significant difference for either display type with respect to correctly detected catheter fragments (mean sensitivity, 56.6% and 56.0% for the CRT and the LCD monitors, respectively, with bright light and 61.2% for both monitors with subdued light). With both display types, detection rate with bright light decreased significantly (P < .05). False-positive rates and confidence ratings were not significantly affected by monitor type or ambient light. CONCLUSION: In a study with simulation of clinical conditions, performance of the LCD monitor and high-resolution CRT monitor for detection of support catheters on bedside chest radiographs was equivalent. With both displays, detection performance was equally reduced with bright ambient light.

Aged↗
PubMed2004

Relation of N-terminal pro-B-type natriuretic peptide to severity of valvular aortic stenosis.

N-terminal pro-B-type natriuretic peptide (NT-proBNP) has been shown to be a reliable biochemical marker for left ventricular wall stress and is increased in patients with aortic stenosis (AS). We evaluated the role of NT pro-BNP as a biochemical marker in the diagnosis of AS and whether it contributes to the optimal timing for aortic valve replacement (AVR). Included in this study were 146 patients who had AS, 31 who underwent AVR, and 32 who had "normal valve function" (controls). Increased NT pro-BNP was closely linked to severity of AS (mild AS 612 +/- 151 pg/ml, moderate AS 1,441 +/- 32 pg/ml, severe AS 2,579 +/- 13 pg/ml, AVR 593 +/- 148 pg/ml, controls 140 +/- 27 pg/ml; p <0,01) and to New York Heart Association functional class (class I 601 +/- 116 pg/ml, class II 1,119 +/- 216 pg/ml, class III 1,998 +/- 459 pg/ml, class IV 5,107 +/- 1,512 pg/ml; p <0.01). Area under the receiver-operating characteristic curve for NT pro-BNP as a predictor for AVR was 0.73. Using an optimized cutoff of 550 pg/ml for NT-proBNP, the positive predictive value was 85%. Thus, NT pro-BNP is linked to severity of AS and New York Heart Association class and is an indication for AVR. Therefore, it is a useful biochemical marker to evaluate severity of AS, monitor disease progression at an early stage, and decide on the optimal time for AVR.

Aged↗
PubMed2004

Comparison of liquid crystal versus cathode ray tube display for the detection of simulated chest lesions.

The purpose of the study was to compare the detection performance of a cathode ray tube (CRT) monitor versus a liquid crystal display (LCD) monitor for simulated subtle pulmonary lesions. Ten templates containing simulated lung lesions were superimposed on an anthropomorphic chest phantom. Posteroanterior radiographs were obtained using flat panel technology and were displayed on a CRT and an LCD monitor. Image processing and reading conditions were equivalent for both softcopy displays. Five observers assessed lesion detectability using receiver-operating characteristic (ROC) methodology. A multivariate test (Pillai trace) was used to test the significance of differences (P<0.05). The multivariate test revealed significantly different detection rates for the lesion types, but no significant difference between the two display modes. Detection performance for both monitors was higher for nodules and micro-nodules and lower for lines and patchy opacities. Analysis of lesion subgroups according to their location in lucent/obscured lung areas was also not statistically significant. Under ideal reading conditions, CRT and LCD displays perform equivalently for the detection of simulated subtle pulmonary lesions.

Data Display↗
PubMed2004

Outcomes in hypertensive patients at high cardiovascular risk treated with regimens based on valsartan or amlodipine: the VALUE randomised trial.

BACKGROUND: The Valsartan Antihypertensive Long-term Use Evaluation (VALUE) trial was designed to test the hypothesis that for the same blood-pressure control, valsartan would reduce cardiac morbidity and mortality more than amlodipine in hypertensive patients at high cardiovascular risk. METHODS: 15?245 patients, aged 50 years or older with treated or untreated hypertension and high risk of cardiac events participated in a randomised, double-blind, parallel-group comparison of therapy based on valsartan or amlodipine. Duration of treatment was event-driven and the trial lasted until at least 1450 patients had reached a primary endpoint, defined as a composite of cardiac mortality and morbidity. Patients from 31 countries were followed up for a mean of 4.2 years. FINDINGS: Blood pressure was reduced by both treatments, but the effects of the amlodipine-based regimen were more pronounced, especially in the early period (blood pressure 4.0/2.1 mm Hg lower in amlodipine than valsartan group after 1 month; 1.5/1.3 mm Hg after 1 year; p<0.001 between groups). The primary composite endpoint occurred in 810 patients in the valsartan group (10.6%, 25.5 per 1000 patient-years) and 789 in the amlodipine group (10.4%, 24.7 per 1000 patient-years; hazard ratio 1.04, 95% CI 0.94-1.15, p=0.49). INTERPRETATION: The main outcome of cardiac disease did not differ between the treatment groups. Unequal reductions in blood pressure might account for differences between the groups in cause-specific outcomes. The findings emphasise the importance of prompt blood-pressure control in hypertensive patients at high cardiovascular risk.

Aged↗
PubMed2004

Plasma levels and redox status of coenzyme Q10 in infants and children.

INTRODUCTION: Increased attention has been paid to the role of lipophilic antioxidants in childhood nutrition and diseases during recent years. The lipophilic antioxidant coenzyme Q10 (CoQ10) is known as an effective inhibitor of oxidative damage. In contrast to other lipophilic antioxidants like alpha-tocopherol the plasma concentrations of CoQ10 in childhood are poorly researched. The aim of this study was to determine plasma level and redox status (oxidized form in total CoQ10 in %) of CoQ10 in clinically healthy infants, preschoolers and school-aged children. METHODS: Plasma level and redox status of CoQ10 were measured by HPLC in 199 clinically healthy children, three groups of infants [1st-4th month (n = 35), 5th-8th month (n = 25), 9th-12th month (n = 25) ], preschoolers (n = 60) and school-aged children (n = 54). The CoQ10 plasma levels were related to plasma cholesterol concentrations. The median and the 5th and 95th percentile were calculated. RESULTS: Plasma levels and redox status of CoQ10 in infants were significantly higher than in preschoolers and school-aged children. The CoQ10 redox status in the 1st-4th month was significantly increased when compared to the remaining subgroups of infants. In elder children the CoQ10 redox status stabilized. CONCLUSIONS: This is the first study concerning age-related values of plasma level and redox status of CoQ10 in apparently healthy children. Decreased CoQ10 values could be involved in various pathological conditions affecting childhood. Therefore, the application of age-adjusted reference values may provide more specific criteria to define threshold values for CoQ10 deficiency in plasma.

Adolescent↗
PubMed2004

N-terminal B-type natriuretic peptide predicts extent of coronary artery disease and ischemia in patients with stable angina pectoris.

BACKGROUND: B-type natriuretic peptide (BNP) and its N-terminal fragment (NT-proBNP) are elevated in patients with acute coronary syndromes and are closely linked to prognosis. Because there is only a small amount of data available concerning NT-proBNP in patients with stable angina pectoris, we aimed to determine whether NT-proBNP is of additional diagnostic value in these patients. METHODS AND RESULTS: Ninety-four patients with stable angina pectoris were prospectively included. All patients underwent exercise testing and coronary angiography, and 91 patients received thallium-201 single-photon emission computed tomography myocardial scintigraphy. NT-proBNP was analyzed at rest and after exercise testing. NT-proBNP was elevated in patients with inducible myocardial ischemia shown by single-photon emission computed tomography (396 +/- 80 pg/mL vs 160 +/- 101 pg/mL; P <.01) closely linked to the extent of coronary artery disease (CAD) (no CAD, 148 +/- 29 pg/mL; 1- or 2-vessel disease, 269 +/- 50 pg/mL; 3-vessel disease 624 +/- 186 pg/mL; P <.01). In a multivariate analysis, NT-proBNP was an independent predictor for CAD. The area under the curve of the receiver operating characteristic curve was 0.72 for NT-proBNP to predict CAD. Using an optimized cut off level of 214 pg/mL, CAD can be predicted with high accuracy. The total test efficiency of exercise testing can be improved from 1.46 to 1.52 when combined with NT-proBNP measurement. CONCLUSION: NT-proBNP is elevated in patients with stable angina pectoris and has a close correlation to disease severity. Combining the measurement of NT-proBNP with exercise testing, the test accuracy for predicting severe CAD can be improved. Our data show an incremental value of NT-proBNP in the diagnostic process of stable angina pectoris.

Aged↗
PubMed2004

Clinical experience with perindopril in African-American hypertensive patients: a large United States community trial.

BACKGROUND: The prevalence of hypertension is greater in African Americans, and management of this condition presents challenges for practicing physicians. METHODS: The effectiveness and safety of perindopril was evaluated in hypertensive African-American patients (n = 1412) and hypertensive white patients (n = 7745) who had participated in a large United States community trial. Patients received perindopril 4 mg once daily for 6 weeks. Based on physicians' clinical judgment at week 6, the dose was either maintained or increased to 8 mg for an additional 6 weeks. RESULTS: Reduction of blood pressure (BP) was significant with perindopril monotherapy (4 to 8 mg once daily) in African Americans and whites (P <.001). The magnitude of BP reduction was significantly more in whites (P <.001). Up-titration of perindopril achieved additional BP reduction in both ethnic groups (P <.001). Control of BP (<140/90 mm Hg) in elderly (>65 years of age) and diabetic African-Americans subgroups was achieved in 32.1% and 31.6%, respectively. Perindopril was safe and well tolerated. CONCLUSIONS: Perindopril monotherapy is effective and is a viable initial therapeutic option as an antihypertensive agent in African-American individuals with hypertension.

Aged↗
PubMed2004

Comparative microarray analysis of Arabidopsis thaliana and Arabidopsis halleri roots identifies nicotianamine synthase, a ZIP transporter and other genes as potential metal hyperaccumulation factors.

The hyperaccumulation of zinc (Zn) and cadmium (Cd) is a constitutive property of the metallophyte Arabidopsis halleri. We therefore used Arabidopsis GeneChips to identify genes more active in roots of A. halleri as compared to A. thaliana under control conditions. The two genes showing highest expression in A. halleri roots relative to A. thaliana roots out of more than 8000 genes present on the chip encode a nicotianamine (NA) synthase and a putative Zn2+ uptake system. The significantly higher activity of these and other genes involved in metal homeostasis under various growth conditions was confirmed by Northern and RT-PCR analyses. A. halleri roots also show higher NA synthase protein levels. Furthermore, we developed a capillary liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry (CapLC-ESI-QTOF-MS)-based NA analysis procedure and consistently found higher NA levels in roots of A. halleri. Expression of a NA synthase in Zn2+-hypersensitive Schizosaccharomyces pombe cells demonstrated that formation of NA can confer Zn2+ tolerance. Taken together, these observations implicate NA in plant Zn homeostasis and NA synthase in the hyperaccumulation of Zn by A. halleri. Furthermore, the results show that comparative microarray analysis of closely related species can be a valuable tool for the elucidation of phenotypic differences between such species.

Alkyl and Aryl Transferases↗
PubMed2004

A 1536-well cAMP assay for Gs- and Gi-coupled receptors using enzyme fragmentation complementation.

Guanosine triphosphate binding protein (G protein)-coupled receptors (GPCRs) are a large class of pharmaceutical drug targets. With the increasing popularity of functional assays for high throughput screening, there arises an increasing need for robust second messenger assays that reflect GPCR activation and are readily amenable for miniaturization. GPCRs that upon agonist stimulation modulate adenylyl cyclase activity, and, consequently, cellular cyclic adenosine monophosphate (cAMP) levels, via the G protein Gs or Gi, form a subset of therapeutic targets. While there are several cAMP assays currently available, most are not scalable for miniaturization into the 1536-well format employed for automated high throughput screening of large chemical libraries. Here, we describe a cAMP assay based on the enzyme fragmentation complementation (EFC) of beta-galactosidase. In this assay, recombinant cells expressing Gs- or Gi-coupled receptors exhibit robust and reproducible pharmacology for agonists and antagonists, as measured by cAMP levels. Furthermore, the EFC cAMP assay offers sufficient sensitivity to be used with cells expressing endogenous GPCRs. We demonstrate the miniaturization of this assay into a 1536-well format with comparable sensitivity and plate statistics to those of the 384-well assay for both Gs- and Gi-coupled receptors, and its suitability for miniaturized high throughput screening.

Animals↗
PubMed2004

Comparison of an automatic versus a semiautomatic mode for gray-scale adaptation for digital chest radiography.

PURPOSE: To compare image quality of digital chest radiographs using 2 modes of gradation adjustment. METHODS: We compared image quality and visualization of anatomic landmarks of 50 chest radiographs after digital processing using a semiautomatic mode with a fixed gamma of 2.6 and an automatic mode with individual gamma adaptation. RESULTS: The mean gamma was significantly higher (P < 0.001) with the automatic mode (3.0 vs. 2.6, respectively). Patient constitution had no impact on the automatically adapted gamma for PA but showed a significant correlation (P < 0.001) for lateral images. For PA, there was a preference (P < 0.016) of the semiautomatic mode in heavier patients whereas no difference was seen in slim patients. For the lateral projection, there was a general preference (P = 0.001) of the automatic mode. CONCLUSION: For PA radiographs, the semiautomatic mode provides superior results for heavier patients without compromising the quality in slim patients. For lateral radiographs, the automatic mode provides generally superior results.

Adult↗
PubMed2004

Antihypertensive utility of perindopril in a large, general practice-based clinical trial.

The authors evaluated, in a community-based open-label trial, the effectiveness and safety of perindopril in 13,220 US hypertensive patients and studied how physicians adhere to hypertension treatment guidelines. Patients received perindopril 4 mg q.d. for 6 weeks. Based on physicians perception of blood pressure response, the patient was either maintained on 4 mg or the dose was increased to 8 mg for an additional 6 weeks. From baseline to week 12, the mean sitting blood pressure significantly declined from 156.9/94.5 mm Hg to 139.2/84.0 mm Hg. Further dose titration resulted in a clinically significant reduction in blood pressure in all patients with inadequate response on 4 mg at week 6. Blood pressure control (<140/<90 mm Hg) was achieved at 12 weeks in 48.8% patients. The subpopulation analyses demonstrated that perindopril monotherapy was effective in both men and women, in patients of all ethnicities, and in patients <65 and > or =65 years of age. Perindopril was safe and well tolerated in all hypertensive subgroups including high-risk patients. Physicians were more attuned to controlling diastolic than systolic blood pressure, and their adherence to the treatment guidelines was found to be not optimal.

Adult↗
PubMed2004

Roundtable discussion: blood pressure goal attainment: meeting the challenge of the JNC 7's blood pressure goals and the role of renin-angiotensin-aldosterone system blockade.

This roundtable discussion, held in December 2003, was convened to discuss the impact of the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure's (JNC 7) challenging blood pressure goal objectives for the clinical management of hypertensive patients. The discussion was moderated by Michael Weber, MD, of the State University of New York Downstate College of Medicine in New York City. Participants included leading experts in the field Joseph Izzo, Jr., MD, of the School of Medicine and Biomedical Sciences at the State University of New York at Buffalo; Suzanne Oparil, MD, of the Vascular Biology and Hypertension Program, Division of Cardiovascular Disease, University of Alabama at Birmingham; and Jan Basile, MD, of the Ralph H. Johnson VA Medical Center and Department of General Internal Medicine/Geriatrics, Medical University of South Carolina in Charleston. The primary intention of this roundtable is to educate physicians about the importance of achieving the blood pressure goals agreed upon by the JNC 7 Committee and to present practical ways for the attainment of such goals in clinical practice.

Antihypertensive Agents↗
PubMed2004

Skeletal applications for flat-panel versus storage-phosphor radiography: effect of exposure on detection of low-contrast details.

PURPOSE: To compare exposure requirements for similar detection performance with flat-panel detectors and the most recent generation of storage-phosphor plates in the simulated scatter of typical skeletal radiographic examinations. MATERIALS AND METHODS: A contrast-detail test object was covered with varying thicknesses of acrylic to simulate skeletal exposure conditions in the wrist, knee, and pelvis. Three series were obtained with increasing thicknesses of a simulated soft-tissue layer (5, 10, and 20 cm) and increasing tube voltage (50, 70, and 90 kVp). A fourth series was obtained with exposure conditions adapted to the phantom instructions (75 kVp). Images were acquired with a flat-panel detector (cesium iodide scintillator) and storage-phosphor plates at five exposure levels (speed class range, 100-1,600). Five readers evaluated 84 images to determine the threshold contrast of 12 lesion diameters (range, 0.25-11.1 mm). Statistical significance of differences between the two digital systems was assessed with two-way analysis of variance. RESULTS: A linear relationship was found between the number of detected lesions and the logarithm of exposure (R(2) > 0.98 for all series). On average, the flat-panel system required 45% less exposure than did the phosphor plates when 20-cm-thick acrylic was superimposed on the test object. Differences in exposure requirements were smaller with decreasing thicknesses of simulated soft-tissue layers and lower tube voltages (39% at 10 cm and 70 kVp, and 17% at 5 cm and 50 kVp). All differences were statistically significant. CONCLUSION: Flat-panel radiography provides improved contrast detectability and a potential for exposure reduction compared with those with storage-phosphor radiography. The best performance was achieved with conditions comparable to those for radiography of the trunk and lowest for conditions that simulate radiography of the extremities.

Bone and Bones↗